1. Field of the Invention
The present invention relates to a pressure releasing mechanism of a fixing device required for processing a paper feeding error (paper jam) in an image forming device such as a copying machine, a printer or the like, and an image forming device using the pressure releasing mechanism.
2. Description of the Related Art
In an image forming device such as a copying machine, a printer or the like where an image is formed on a paper sheet, a path to feed paper sheets (paper path) is arranged inside of the device, and by a paper feed roller in this paper path, paper sheets are fed to an image forming unit that forms a toner image on paper sheets, and a fixing unit that heats the toner image formed on paper sheets and pressurizes and fixes it onto paper sheets, and then paper sheets are discharged to the outside of the device. However, paper sheets may not be in ideal conditions for the device in many cases, and owing to changes in paper sheet conditions such as high humidity, curling, and the like, and conditions of the paper feed roller and the paper path, an error (jam) accidentally occurs where papers stop in the paper path.
At occurrence of this jam, it is necessary for a user to remove jammed paper sheets from the paper path, and especially in a fixing device, because paper sheets go through between a heat roller and a pressure roller to which a predetermined pressure is added, if a jam occurs while paper sheets go between them, it is required to release the pressure that is added between the rollers.
As this pressure releasing means, there is disclosed an art to release pressure by pressing/releasing a frame supporting a heat roller by a cam, and easily remove paper sheets (for example, Jpn. Pat. Appln. KOKAI Publication No. 2002-311743).
However, in such a pressure releasing method by rotating a cam as disclosed in the above Jpn. Pat. Appln. KOKAI Publication No. 2002-311743, it is necessary to rotate the cam electrically by a device, or manually by a user. In the former case, a motor for rotating the cam for processing a jam error is required, which increases costs. Further, in the latter case, it is required for a user to carry out a troublesome operation. In this jam processing, there are many operation procedures including opening a cover, rotating a cam, and so forth, and an inexperienced user frequently makes mistakes in the procedures, as a result, paper sheets cannot be removed easily, and further, there is a fear a user may try removing paper sheets forcibly without knowing correct procedures, and destroy the device.